The present invention relates to an ultrasonic diagnostic equipment having a synthetic aperture receiving portion or a fold over portion of received signals.
An ultrasonic imaging apparatus for performing synthetic aperture scanning is known recently. This ultrasonic imaging apparatus has been introduced in P.D. Corl, et al. "A digital synthetic focus acoustic imaging system for NDE", Proc IEEE Ultrasonics Symp., Sept. 1978, and the principle of the operation thereof will be described with reference to a schematic block diagram shown in FIG. 8.
In FIG. 8, a reference numeral 1 represents an ultrasonic probe, which is composed of piezoelectric transducers T1 to T8. 100 represents a multiplexer (hereinafter referred to as a MUX), 101 a transmitting circuit, 102 an amplifier, 103 an A/D converter (hereinafter referred to as an A/D), 104 a memory, 105 an adder, 106 a signal processor and 107 a display unit. In FIG. 8, the MUX 100 selects one of the piezoelectric transducers T1 to T8, i.e., Tn. Next, the transmitting circuit 101 generates driving pulses, thereby to drive the selected piezoelectric transducer Tn.
The piezoelectric transducer Tn generates ultrasonic pulses, and the ultrasonic pulses reflected in an object are received by the piezoelectric transducer Tn as an echo ultrasonic wave. The received signals received by the piezoelectric transducer Tn are converted into digital data in the A/D 103 and written in the memory 104 after passing through the MUX 100 and being amplified by the amplifier 102. When the write of the received signals into the memory 104 from the piezoelectric transducer Tn is completed, then the MUX 100 selects a piezoelectric transducer Tn' different from the piezoelectric transducer Tn, and writes the received signals into the memory 104 in a similar manner as the case of the piezoelectric transducer Tn. In a manner as described above, the received signals obtained by the piezoelectric transducers T1 to T8 are written into the memory 104. Next, in the adder 105, respective received signals obtained from the piezoelectric transducers T1 to T8 that are stored in the memory 104 are added while providing them with a predetermined time difference.
When it is assumed that the object is at a standstill during the period of reception by the piezoelectric transducers T1 to T8, it is possible to give receiving directivity such as beam forming and beam steering in the object to the ultrasonic probe 1. The received signals added by the adder 105 as described above are applied with signal processing such as detection by the signal processor 106 and displayed on the display unit 107.
In the above-mentioned conventional ultrasonic diagnostic equipment having a synthetic aperture portion, however, there has been such a problem that the synthetic aperture portion cannot be operated accurately when the object has moved during the period of reception by the piezoelectric transducers T1 to T8.